1 /* 2 * Author: Rafael da Mata Neri <rafael.neri (at) gmail.com> 3 * Copyright (c) 2015 Intel Corporation. 4 * 5 * Permission is hereby granted, free of charge, to any person obtaining a copy of 6 * this software and associated documentation files (the "Software"), to deal in 7 * the Software without restriction, including without limitation the rights to 8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of 9 * the Software, and to permit persons to whom the Software is furnished to do so, 10 * subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be included in all 13 * copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS 17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR 18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 21 */ 22 #pragma once 23 24 #include <unistd.h> 25 #include <stdlib.h> 26 #include <stdint.h> 27 #include <string.h> 28 #include <mraa/gpio.h> 29 30 namespace upm { 31 /** 32 * @brief HX711 24-bit ADC library 33 * @defgroup hx711 libupm-hx711 34 * @ingroup generic gpio electric 35 */ 36 37 /** 38 * @library hx711 39 * @sensor hx711 40 * @comname HX711 Analog-to-Digital Converter 41 * @type electric 42 * @man generic 43 * @web http://www.dfrobot.com/image/data/SEN0160/hx711_english.pdf 44 * @con gpio 45 * 46 * @brief API for the HX711 Analog-to-Digital Converter 47 * 48 * HX711 is a precision 24-bit analog-to-digital converter (ADC) 49 * designed for weight scales and industrial control applications to 50 * interface directly with a bridge sensor. This module was tested on 51 * the Intel(R) Galileo Gen 2 board. 52 * 53 * @image html hx711.jpeg 54 * @snippet hx711.cxx Interesting 55 */ 56 class HX711 { 57 public: 58 /** 59 * HX711 constructor 60 * 61 * @param data Defines the data pin 62 * @param sck Defines the clock pin 63 * @param gain Defines the gain factor 64 * Valid values are 128 or 64 for channel A; channel B works with a 32-gain factor only 65 */ 66 HX711(uint8_t data, uint8_t sck, uint8_t gain = 128); 67 68 /** 69 * HX711 destructor 70 */ 71 ~HX711(); 72 73 /** 74 * Waits for the chip to be ready and returns a reading 75 * 76 * @return Raw ADC reading 77 */ 78 unsigned long read(); 79 80 /** 81 * Sets the gain factor; takes effect only after a call to read() 82 * channel A can be set for a 128 or 64 gain; channel B has a fixed 32-gain 83 * factor depending on the parameter; the channel is also set to either A or B 84 * @param gain Defines the gain factor 85 */ 86 void setGain(uint8_t gain = 128); 87 88 /** 89 * Returns an average reading 90 * @param times Defines how many reading to do 91 * @return Average reading 92 */ 93 unsigned long readAverage(uint8_t times = 10); 94 95 /** 96 * Returns (readAverage() - OFFSET) 97 * @param times Defines how many readings to do 98 * @return Current value without the tare weight 99 */ 100 double getValue(uint8_t times = 10); 101 102 /** 103 * Returns getValue() divided by SCALE 104 * @param times Defines how many readings to do 105 * @return Raw value divided by a value obtained via calibration 106 */ 107 float getUnits(uint8_t times = 1); 108 109 /** 110 * Sets the OFFSET value for the tare weight 111 * @param times Defines how many times to read the tare value 112 */ 113 void tare(uint8_t times = 10); 114 115 /** 116 * Sets the SCALE value 117 * This value is used to convert the raw data to human-readable data (measurement units) 118 * @param scale Value obtained via calibration 119 */ 120 void setScale(float scale = 1.f); 121 private: 122 mraa_gpio_context m_sckPinCtx; // Power Down and Serial Clock Input Pin 123 mraa_gpio_context m_dataPinCtx; // Serial Data Output Pin 124 125 uint8_t GAIN; // amplification factor 126 unsigned long OFFSET; // used for tare weight 127 float SCALE; // used to return weight in grams, kg, ounces, whatever 128 129 130 /** 131 * Sets the OFFSET value 132 * This value is subtracted from the actual reading (tare weight) 133 * @param scale Value obtained via calibration 134 */ 135 void setOffset(long offset = 0); 136 }; 137 138 } 139
